1. Field of the Invention
Embodiments of the invention generally relate to semiconductor substrate processing systems. More particularly, embodiments of the invention relate to methods and apparatus for delivering gases into a processing chamber.
2. Description of the Related Art
Materials such as oxides are typically deposited on a substrate within a process chamber, such as a chemical vapor deposition (CVD) chamber, during fabrication of integrated circuits and semiconductor devices. A gas distribution plate or faceplate of the deposition chamber includes a plurality of spaced holes that process gases pass through to aid in distributing the materials in the chamber. The deposition processes typically result in deposition of some of the materials on walls and components of the deposition chamber. For example, a layer of deposition material often forms on the gas distribution plate, which may clog the holes of the plate or flake off in particles that rain down on the substrate, thereby affecting the uniformity of deposition on the substrate and contaminating the substrate. Consequently, the interior of the deposition chamber requires cleaning on a regular basis.
There exist several methods for cleaning the deposition chamber including the gas distribution plate using cleaning gases. For example, a remote plasma cleaning procedure may be employed using an etchant plasma generated remotely from the deposition chamber by introduction of an etchant gas such as a fluorine containing gas to a remote high density plasma source, which may be a microwave plasma system, a toroidal plasma generator or a similar device. Dissociated species from the etchant plasma transported to the deposition chamber react with and etch away the undesired deposition build up. Another method to remove the unwanted deposition material that builds up on the interior of chamber walls involves an in situ chamber clean operation. Common in situ chamber cleaning techniques include the use of an etchant gas such as a fluorine containing gas to remove the deposited material from the chamber walls and other areas. The etchant gas is introduced into the chamber and plasma is formed within the chamber so that the etchant gas reacts with and removes the deposited material from the chamber walls.
In prior CVD chambers, both the process gases and the cleaning gases pass through a common feed path to a blocker plate that aids in uniformly distributing the gases prior to their passage through the gas distribution plate. Some deposition processes operate at reduced flow significantly reducing chamber cleaning efficiency when the cleaning gases are passed through the common feed that is adapted for the reduced flow. The lower clean efficiency increases the amount of time it takes to clean the chamber, increases the amount of cleaning gases consumed, and reduces the number of substrates that can be processed in a given time (i.e., throughput).
One design that enables the cleaning gases to bypass the blocker plate routes all of the cleaning gases to a periphery of the gas distribution plate in order to increase the cleaning rate at the perimeter of the chamber compared to the center of the chamber. However, the center of the chamber may not be sufficiently cleaned with all the cleaning gases directed to the periphery of the gas distribution plate.
Therefore, a need exists for apparatus and methods for delivering gases into a chamber that enables independent control of processing gases and cleaning gases. A further need exists for apparatus and methods for controlling the ratio of cleaning gases directed toward the center of the chamber and the perimeter of the chamber.